Characteristics of Life 9/24 Title, date in notebook – required notes Paraphrase what is here – your own words! Available on my website (as are most PowerPoints/presentations)

Disclaimer! These ideas can be organized in different ways 8 characteristics (according to your textbook) Could combine 2 characteristics to get a list of 7 Could expand a few to get a list of 10… Some characteristics are clear/straightforward; others are a bit “messy” Some organisms don’t neatly meet the characteristics!

All living things… Write the words, “All Living Things:” Record each characteristic and brief notes. Paraphrase what we discuss!

Made up of cell(s) What is a cell? Collection of living matter surrounded by a barrier Barrier separates it from its surroundings Living organisms are either: Unicellular One cell (bacteria, some algae) Multicellular More than one cell (most species) All cells contain water Complex organisms can have hundreds of types of cells!

Reproduce (without completely relying on other organisms) What is reproduction? Creation of new organism(s) that meet all characteristics of life Species must be capable of reproduction Types of reproduction? Asexual – One cell/organism “splits”, forms cells that are (mostly) genetically identical Sexual – Two cells from two parents come together to make a new organism Viruses not alive (?) Need host organisms to reproduce (this can be a gray area)

Are based on a genetic code All living things contain either DNA or RNA (or both) DNA/RNA contains the instructions necessary for life processes Instructions for proteins

Take in materials/energy, Produce waste Examples? Take in: oxygen, sunlight, food, water, Produce: Carbon dioxide, methane, oxygen, water Living things do not all need oxygen! Some are anaerobic – no oxygen

Grow and develop At some point in their lives, organisms: Grow larger, develop new features Not all living things have differentiated tissue (e.g., brain, hearts, lungs) Complex organisms experience differentiation  new types of tissues Simple organisms  no differentiation (cells/tissues all same)

Respond to their environment All living things respond to some (few or many) stimuli in their environment Examples? Respond to smells, sights, sounds, physical stimuli, environmental conditions Totally unresponsive to all stimuli = not living

Maintain an internal balance Homeostasis? Responding to your environment to keep your internal balance in some stable range over time. Examples? 1) exercise, red face to let heat out; cold, shiver to warm up; 2) low light, pupils dilate to allow same amount of light in; 3) splashing water on face, heart rate lowers All living things maintain SOME time of internal balance If an object’s internal conditions are always the same as its external environment, not alive!

As a species, evolve over time Evidence supports – all living species have changed over time Some slowly, some quickly Every species evolves over long periods of time Evolve: DNA of a species change over time – new characteristics develop

So, were the 7 items alive? On the board…we’ll split into 4 categories (based on feedback yesterday) Alive Show all 8 characteristics Nonliving Never showed all 8 characteristics Dormant Has the potential to show all 8 characteristics Dead One showed, but no longer show, all 8 characteristics